Fixes #145 changes canonicalization method for metadata xml signature generation

Author: Dave Handy

core/src/main/java/com/onelogin/saml2/util/Util.java

@@ -1106,7 +1106,7 @@ public static String addSign(Document document, PrivateKey key, X509Certificate
 
 		// document.normalizeDocument();
 
-		String c14nMethod = Constants.C14N_WC;
+		String c14nMethod = Constants.C14NEXC_WC;
 
 		// Signature object
 		XMLSignature sig = new XMLSignature(document, null, signAlgorithm, c14nMethod);